You will need rsync and git. You will need to rebuild neon29.
All directories should be /compat/linux/<directory>.
You will need to enable linprocfs, procfs, and linsysfs.
You will need to load lindev and linux.
Use --with-arch=x86.
This build will only work on x86.

The build will stop at an error with /proc.

I'm posting this here because I am working on the build and this will make it easier for others to do the same.

Edit: Didn't have Java installed.
You must use gmake.

Correct the first error in libreoffice/bin/ooinstall with adding /compat/linux to /proc/meminfo at line 34.

Edit 2: In bin, edit setup to include the entire directory path for solenv. Even if you use gmake install, you will need to edit these files.

Yes and no.
The source from the website requires a Linux environment. The port version is what the maintainers modified to work with FreeBSD.
You could install libreoffice to the ppc, x86, and amd platforms for NetBSD.

Neither ports nor packages let you have complete control over the build.

At least with this method, I can install it as a Linux binary in the Linux directory. Branding it as such would be the next step.

I gave up on this. Why? because when it was no longer at the original section, I assumed that it had been deleted.
Whoever want, can completely remove this thread. I consider it a waste of my time even trying such when everyone doesn't believe an alternative method is possible.